Cooling system

ABSTRACT

A cooling system having a pumped loop cooling system and an embedded vapor compression loop system for cooling air inside an enclosed space such as a container both when the required air temperature inside container is warmer or cooler than the outside ambient air temperature. The pumped loop cooling system is positioned within the container except for a condenser positioned outside the container. The vapor compression loop system is positioned outside the container and includes a liquid to liquid heat exchanger which cools the fluid in the pumped loop system when the condenser is selectively bypassed when the temperature inside the container is higher than the temperature outside the container.

TECHNICAL FIELD

The present invention relates generally to cooling air inside anenclosed space that is used to cool components within that space such aspower electronics, batteries, etc., and more particularly to a methodand apparatus for cooling the air inside the container both when therequired air temperature inside container is warmer or cooler than theoutside ambient air temperature.

BACKGROUND

Power electronic devices, such as IGBTs, SCRs, etc., continue to achievehigher power switching capacity in a smaller envelope. The amount ofheat created by these devices continues to climb as well. Conventionalcooling methods include using blowing air, or circulating a water-basedfluid through cold plates in thermal contact with the electronic deviceheat sink. A more recent cooling method utilizes a phase change fluid,or refrigerant, that will evaporate to remove heat from an electronicdevice heat sink, and condense back to liquid state through heatexchange process with a cold medium (air or water).

In a typical prior art two-phase pumped loop cooling system. Liquidrefrigerant enters the pump, where static pressure is raised and flow isinduced. Sub-cooled liquid flows into an evaporator. The evaporator maybe in the form of a cold plate mounted in contact with the heat sink ofan electronic device. Refrigerant fluid absorbs heat from the electronicdevice and partially evaporates as it flows through the cold plate.Partially evaporated refrigerant fluid is collected in a manifold, andthen flows in the condenser heat exchanger. The condenser heat exchangermay be air cooled or water cooled and it may be located indoors oroutdoors. For the condenser to reject heat to a cold medium, therefrigerant fluid temperature must be above that of the cold medium, orthe ambient air. Since the refrigerant is undergoing a condensingprocess, the refrigerant pressure will follow the refrigeranttemperature based on the fluid's saturation pressure-temperaturerelationship. The refrigerant fluid will leave the condenser as asubcooled liquid, the temperature will be above ambient, and thepressure will correspond to an even higher saturation temperature. Thesub-cooled liquid flows into a receiver tank which acts a storage tankto compensate for varying volumes of the fluid in the system. Therefrigerant fluid volume of liquid and vapor will vary throughout thesystem based on operating temperatures and heat load, due to varyingdensities through the operating temperature range.

A problem exists in these prior art systems when the power electronicsare located indoors or in a container and the condenser heat exchangeris located outdoors and exposed to extreme cold temperatures. Since therefrigerant fluid temperature will closely follow the condenser ambientair, there will be conditions where the refrigerant fluid entering backindoors will be cold enough to cool the refrigerant fluid conduitsurface temperature to a level below the indoor air dew point therebycausing condensation on the fluid conduits and other system componentsfrom the moisture of the indoor air. This moisture can drip onto theelectronic devices and cause damage from short circuiting.

SUMMARY

At least one embodiment of the invention provides a cooling systemcomprising: a pumped loop cooling system comprising an evaporator, and apump located in a first environment having a first ambient temperatureand a first compressor located in a second environment having a secondambient temperature; a vapor compression system comprising an expansionvalve, a second condenser, a compressor, and a liquid to liquid heatexchanger, the vapor compression system located in the secondenvironment; a primary fluid conduit through which a first refrigerantfluid is circulated by the pump through the evaporator, to the firstcondenser, and back to the pump; a secondary fluid conduit selectivelydiverting the first refrigerant fluid from the evaporator to the liquidto liquid heat exchanger of the vapor compression system and back to thepump; and a third fluid conduit through with a second refrigerant fluidis circulated from the compressor to the liquid to liquid heatexchanger, to the expansion valve, to the second condenser, and back tothe compressor.

At least one embodiment of the present invention provides a coolingsystem comprising: a pumped loop cooling system comprising anevaporator, a first liquid receiver, and a pump located in a firstenvironment having a first ambient temperature and a first compressorlocated in a second environment having a second ambient temperature; avapor compression system comprising an expansion valve, a secondcondenser, a second liquid receiver, a compressor, and a liquid toliquid heat exchanger, the vapor compression system located in thesecond environment; a primary fluid conduit through which a firstrefrigerant fluid is circulated by the pump through the evaporator, tothe first condenser, to the first liquid receiver, and back to the pump;a secondary fluid conduit selectively diverting the first refrigerantfluid from the evaporator to the liquid to liquid heat exchanger of thevapor compression system, to the liquid receiver, and back to the pump;and a third fluid conduit through with a second refrigerant fluid iscirculated from the compressor to the liquid to liquid heat exchanger,to the expansion valve, to the second liquid receiver, to the secondcondenser, and back to the compressor.

At least one embodiment of the invention provides a cooling systemcomprising: a pumped loop cooling system comprising an evaporator, afirst liquid receiver, and a pump located in a first environment havinga first ambient temperature and a first compressor located in a secondenvironment having a second ambient temperature; a vapor compressionsystem comprising an expansion valve, a second condenser, a secondliquid receiver, a compressor, and a liquid to liquid heat exchanger,the vapor compression system located in the second environment; aprimary fluid conduit through which a first refrigerant fluid iscirculated by the pump through the evaporator, to the first condenser,to the first liquid receiver, and back to the pump; a secondary fluidconduit selectively diverting the first refrigerant fluid from theevaporator to the liquid to liquid heat exchanger of the vaporcompression system, to the liquid receiver, and back to the pump; and athird fluid conduit through with a second refrigerant fluid iscirculated from the compressor to the liquid to liquid heat exchanger,to the expansion valve, to the second liquid receiver, to the secondcondenser, and back to the compressor; a control system adapted todirect the first refrigerant through the first conduit to the firstcondenser and to bypass the second conduit when the temperature in thefirst environment is higher than the temperature in the secondenvironment; the control system adapted to direct the first refrigerantthrough the second conduit and bypass a portion of first conduitincluding the first condenser and operating the compressor of the vaporcompression system when the temperature in the first environment ishigher than the temperature in the second environment.

BRIEF DESCRIPTION OF THE DRAWING

Embodiments of this invention will now be described in further detailwith reference to the accompanying drawings, in which:

FIG. 1 is a schematic view of an embodiment of the cooling system of thepresent invention.

DETAILED DESCRIPTION OF THE DRAWING

Referring to the drawing in detail, the cooling system 10 comprises apumped loop cooling system 20 and an imbedded vapor compression system22. The pumped loop cooling system 20 comprising at least one evaporator30, a first liquid receiver 32, and at least one pump 34 located in afirst environment 40 (represented as a box) having a first ambienttemperature and a first condenser 36 located in a second environment 42(outside the box) having a second ambient temperature—all connected by afirst fluid conduit 8. The vapor compression system 22 is located in thesecond environment 42 and comprises an expansion valve 44, a secondcondenser 46, a second liquid receiver 48, a compressor 50, and a liquidto liquid heat exchanger 52—all connected by a third fluid conduit 6.

In operation, the one or more liquid pumps 34 circulate refrigerantfluid through the pumped loop cooling system 20 portion of the coolingsystem 10. The fluid flows through one or more evaporators 30, eachshown with an associated fan 31 to assist the evaporator in theabsorption of heat from the air inside the enclosed space designated andreferred to as the first environment 40. The absorption of the heatpartially boils the refrigerant fluid. The two-phase fluid is thenrouted outside the first environment 40 to second environment 42. If theoutside ambient temperature is much colder than the required airtemperature within the enclosed space 40, the fluid is routed throughcondenser 36 where the fluid is cooled back to a liquid by means ofblowing cooler ambient air across the condenser coil. If the outsideambient air temperature is nearly the same or warmer than the requiredenclosed space temperature, fluid is diverted through a secondaryconduit or bypass conduit 9 by one or more valves 56, 54 to a liquid toliquid heat exchanger 52. The heat is transferred to the secondaryrefrigerant loop comprising vapor compression system 22. The vaporcompression system 22 includes compressor 50 and expansion valve 44which allow for that fluid circuit to remain below outside ambienttemperature. The vapor compression loop 22 only turns on whensub-ambient cooling is needed. The heat from the vapor compression loop22 is rejected to the outdoor ambient air by means of a condenser coil46 and a fan 47. Because heat is only being rejected from one of the twocondensing coils 36, 46 at a given time, the condensing coils 36, 46 maybe interlaced together, although the fluids would remain separate andnot mix. This also means the two condensing coils 36 may share the samefan 47 and fan enclosure 49.

The system 10 includes a control system 60 based on the temperaturewithin the enclosed space and optionally the outdoor ambient temperatureto determine when to switch to the vapor compression system. The controlsystem 60 may be adapted to direct the first refrigerant through thefirst conduit 8 to the first condenser 36 and to bypass the secondconduit 9 (utilizing valves 54, 56) when the temperature in the firstenvironment 40 is higher than the temperature in the second environment42. The control system 60 may be adapted to direct the first refrigerantthrough the second conduit 6 and bypass a portion of first conduit 8including the first condenser 36 and selectively operating thecompressor 50 of the vapor compression system when the temperature inthe first environment 40 is higher than the temperature in the secondenvironment 42. The control system 60 may be adapted to selectivelyactivate the compressor 50 when the temperature of the secondenvironment 42 is higher than the temperature of the first environment40 and to deactivate the compressor 50 when temperature of the secondenvironment 42 is lower than the temperature of the first environment40.

The system 10 also allows for complete bypass of all condensing byallowing all of the pumped system flow to go through the liquid toliquid heat exchanger 52 without the vapor compression system 22running. In this mode, there would be no cooling of the fluid. This isnecessary when there is only a light heat load on the cooling system anda cold outside ambient temperature.

Furthermore, in some applications it may be required to initially heatthe enclosed space ambient air on initial start-up in cold ambientenvironments. This is usually just temporary until the devices needingcooled can create enough heat on their own to maintain a warmer enclosedspace temperature. The vapor compression loop 22 can be designed as aheat pump loop, where it can run in reverse when needed to put heat intothe system and thus reject hot air into the enclosed space.

Although the invention has been shown and described with respect to acertain preferred embodiment or embodiments, it is obvious thatequivalent alterations and modifications will occur to others skilled inthe art upon the reading and understanding of this specification and theannexed drawings. In particular regard to the various functionsperformed by the above described elements (components, assemblies,devices, compositions, etc.), the terms (including a reference to a“means”) used to describe such elements are intended to correspond,unless otherwise indicated, to any element which performs the specifiedfunction of the described element (i.e., that is functionallyequivalent), even though not structurally equivalent to the disclosedstructure which performs the function in the herein illustratedexemplary embodiment or embodiments of the invention. In addition, whilea particular feature of the invention may have been described above withrespect to only one or more of several illustrated embodiments, suchfeature may be combined with one or more other features of the otherembodiments, as may be desired and advantageous for any given orparticular application.

1. A cooling system comprising: a pumped loop cooling system comprisingan evaporator, and a pump located in a first environment having a firstambient temperature and a first compressor located in a secondenvironment having a second ambient temperature; a vapor compressionsystem comprising an expansion valve, a second condenser, a compressor,and a liquid to liquid heat exchanger, the vapor compression systemlocated in the second environment; a primary fluid conduit through whicha first refrigerant fluid is circulated by the pump through theevaporator, to the first condenser, and back to the pump; a secondaryfluid conduit selectively diverting the first refrigerant fluid from theevaporator to the liquid to liquid heat exchanger of the vaporcompression system and back to the pump; and a third fluid conduitthrough with a second refrigerant fluid is circulated from thecompressor to the liquid to liquid heat exchanger, to the expansionvalve, to the second condenser, and back to the compressor.
 2. Thecooling system of claim 1, wherein the first refrigerant fluid isselectively diverted to the secondary fluid conduit by at least onevalve.
 3. The cooling system of claim 2, wherein the at least one valvediverts the first refrigerant fluid to the secondary fluid conduit whenthe first ambient temperature is greater than the second ambienttemperature
 4. The cooling system of claim 2, wherein the at least onevalve is a first and a second two-way valve positioned in parallel witheach other.
 5. The cooling system of claim 4, wherein the first two wayvalve is located in the primary fluid conduit upstream of the firstcondenser and downstream of the evaporator.
 6. The cooling system ofclaim 4, wherein the first two way valve is located in the secondenvironment.
 7. The cooling system of claim 4, wherein the second twoway valve is located in the secondary fluid conduit upstream of theliquid to liquid heat exchanger and downstream of the evaporator.
 8. Thecooling system of claim 4, wherein the second two way valve is locatedin the second environment.
 9. The cooling system of claim 1 furthercomprising a liquid receiver located in the first environment upstreamof the pump.
 10. The cooling system of claim 1, wherein the vaporcompression system further comprises a liquid receiver locateddownstream from the expansion valve and upstream of the secondcondenser.
 11. The cooling system of claim 1, wherein the evaporatorincludes a fan.
 12. The cooling system of claim 1, wherein the firstcondenser includes a fan.
 13. The cooling system of claim 12, whereinthe second condenser is positioned adjacent the first condenser andshares the fan of the first condenser.
 14. The cooling system of claim 1further comprising a control system operable to selectively divert therefrigerant fluid from the primary fluid conduit to the secondary fluidconduit when the first ambient temperature is greater than the secondambient temperature.
 15. The cooling system of claim 1, wherein thesecond refrigerant fluid is selectively flowed through the third conduitin reverse and the heat exchanger, the expansion valve, the secondcondenser, and the compressor of the secondary fluid conduit act as aheat pump rejecting heat from the second refrigerant to the firstrefrigerant at the liquid to liquid heat exchanger.
 16. The coolingsystem of claim 1, wherein the refrigerant is selectively diverted tothe secondary fluid conduit without operation of the vapor compressionsystem.
 17. A cooling system comprising: a pumped loop cooling systemcomprising an evaporator, a first liquid receiver, and a pump located ina first environment having a first ambient temperature and a firstcompressor located in a second environment having a second ambienttemperature; a vapor compression system comprising an expansion valve, asecond condenser, a second liquid receiver, a compressor, and a liquidto liquid heat exchanger, the vapor compression system located in thesecond environment; a primary fluid conduit through which a firstrefrigerant fluid is circulated by the pump through the evaporator, tothe first condenser, to the first liquid receiver, and back to the pump;a secondary fluid conduit selectively diverting the first refrigerantfluid from the evaporator to the liquid to liquid heat exchanger of thevapor compression system, to the liquid receiver, and back to the pump;and a third fluid conduit through with a second refrigerant fluid iscirculated from the compressor to the liquid to liquid heat exchanger,to the expansion valve, to the second liquid receiver, to the secondcondenser, and back to the compressor.
 18. The cooling of claim 17further comprising: a control system adapted to direct the firstrefrigerant through the first conduit to the first condenser and tobypass the second conduit when the temperature in the first environmentis higher than the temperature in the second environment; the controlsystem adapted to direct the first refrigerant through the secondconduit and bypass a portion of first conduit including the firstcondenser and selectively operating the compressor of the vaporcompression system when the temperature in the first environment ishigher than the temperature in the second environment.
 19. A coolingsystem comprising: a pumped loop cooling system comprising anevaporator, a first liquid receiver, and a pump located in a firstenvironment having a first ambient temperature and a first compressorlocated in a second environment having a second ambient temperature; avapor compression system comprising an expansion valve, a secondcondenser, a second liquid receiver, a compressor, and a liquid toliquid heat exchanger, the vapor compression system located in thesecond environment; a primary fluid conduit through which a firstrefrigerant fluid is circulated by the pump through the evaporator, tothe first condenser, to the first liquid receiver, and back to the pump;a secondary fluid conduit selectively diverting the first refrigerantfluid from the evaporator to the liquid to liquid heat exchanger of thevapor compression system, to the liquid receiver, and back to the pump;and a third fluid conduit through with a second refrigerant fluid iscirculated from the compressor to the liquid to liquid heat exchanger,to the expansion valve, to the second liquid receiver, to the secondcondenser, and back to the compressor; a control system adapted todirect the first refrigerant through the first conduit to the firstcondenser and to bypass the second conduit when the temperature in thefirst environment is higher than the temperature in the secondenvironment; the control system adapted to direct the first refrigerantthrough the second conduit and bypass a portion of first conduitincluding the first condenser and operating the compressor of the vaporcompression system when the temperature in the first environment ishigher than the temperature in the second environment.